The dependence on imported mineral oil, the long-term shortage and the increase in price connected therewith of raw materials produced from mineral oil has initiated a world-wide search for hydrocarbon-containing raw materials. Since the supplies of coal clearly exceed the reserves of mineral oil, the concerned branches of industry and Government in countries with large coal deposits are striving to develop new feasible processes for refinement of coal to make these raw materials available. With that, it is possible to build on a broad base a knowledge, for the coal-chemical industry currently produces world-wide more than 20 million tons of coal refinement products. Quantitatively, the most important product of coal chemistry refining is coal tar pitch, the residue obtained from coal tar distillation. Coal tar pitch is used as a high grade raw material, especially for the production of electrodes and other types of artificial carbon, as a binder and structural building material. Other binders based on coal tar pitch are used, for example, in bituminous road construction, for the production of fire resistant stones and moulded coke for improvement of coking coal and for insulating materials for the building industry, wherein for these areas of application the ash content is of subordinate significance.
Because of the limited availability of coal tar pitch, attempts have been made to use other petroleum residues or residues of coal origin for the above mentioned fields of application. With regard to residues of petroleum origin, supply difficulties are to be expected in the future since, as explained previously, the petroleum reserves are shrinking drastically in the course of time. On the basis of coal, so-called "solvent refined coal products" (SRC-products) are proposed as pitch substitutes (cf. for example, Japan Kokai 78 88 001, C. A. 89, 217860c). These processes for the partial hydrogenation of coal provide for the use of molecular hydrogen in quantities of 2-4% and are correspondingly expensive; moreover, they do not lead to a highly aromatic product, since aliphatic portions also participate in the make-up of the coal which are not aromatized at the temperature customarily employed in coal hydrogenation.
A similar process is described for example, in the South African patent 74 03326 (C.A. 87, 8541u). As a solvent for the coal slurry preparation, heavy creosote oil or anthracene oil are mentioned. The mixture used is also subjected in that instance to the conditions of a hydrogenation with H.sub.2. Beyond that, for example, Japan Kokai No. 78 96003 (C.A. 89,217864g) discloses a process for obtaining a "pitch" from coal by disintegration with a mixture of heavy oil, which is obtained by heat treatment of fuel oil at 350.degree.-450.degree. C., and tar acids, that is, phenols. The yield of disintegration coal, could be increased by the combination with the tar acids. These processes or the obtainable "pitch" have the following disadvantages:
Instead of the expensive molecular hydrogen, in this case likewise valuable chemical raw materials, namely phenols, are used for the disintegration of the coal. The same is true also for the use of anthracene oil and creosote oil. These oils generally must be recaptured by distillation and have strongly changed their chemical composition as a result of the transferring of hydrogen. Furthermore, the case of using molecular hydrogen, catalysts are needed as a rule, for example, iron or cobalt-molybdenum-oxide catalysts (see, U.S. Pat. No. 4,021,329; C.A. 87,258856).